Virgin brass vs. fire formed

[jrob300]

There may be other issues at play here. Last time I talked to one of the Sierra tech guys, I mentioned that I had just bought 300 rds. of Win. brass and had to neck turn it because it varied from .0115 to .017 on the necks. He asked me if I fireformed my brass. I thought, "Huh?" I only thought those AI guys did that stuff. He told me that he had 7mm Mag. brass that was on its 18th or 19th firing (I forget)because the first time he fired it, he loaded the bullets into the lands so that the case did not stretch above the belt.

According to him, if you don't put the bullet in the lands the first firing, the firing pin pushes the case forward to the shoulder (w/ virgin win. brass that's a long way) the case expands upon ignition and grips the walls of the chamber, then the case stretches above the belt (I imagine non-belted cases do the same thing) as the base of the case is rammed back into the bolt face. Seems very dramatic.

Have you guys heard of this. Makes sense on paper. Seems like a lot of work. I'm poised with 300 virgin brass. Do I fireform or not?

Thanks

John

 

[Frogman77]

I don't know, like I said I"m still new at this, but from the 2 lots of new win brass that I loaded for my .30-06 the new brass measured about .015" short of min spec. After firing my case stretched almost .020" which seemed like a lot. My groups on that first firing were terrible, but my once fired/fireformed brass did way better... That was enough for me to decide to fireform my cases with cheapo bullets before testing for accuracy or load development.

 

[bigngreen]

I started fire forming my 270WSM after having problems with full tilt loads sticking my bolt with new brass. It looked like the brass was full forward when fired then the primer would push back then the case would slam back, after the first firing I can FL size and have no problems. I kinda wonder if it has more to do with head spacing and how close to min spec the chamber is, both of which I don't know where mine is at.

 

[Jinx-)]

Today at the range interesting thing happen I had fire-formed brass which been fired at least 5 or 7 times, also 2 weeks ago it consistently held 0.2 MOA, but then last week I got few fliers, so I got some loads using virgin brass, today I fired both and the results at 300 yards were: virgin 0.25 MOA and old fire-formed 0.82 MOA, then I tired them at 100 yards and new brass scored 0.28" and old fire-formed 1.2", this is the same brass which shot one hole groups 2 weeks ago... I'm puzzled with these results...

 

[Pdvdh]

The neck tension with the 7x fired cases could be the culprit. Work the case necks through the sizing process that many times and the necks will stiffen up on you. You could anneal those case necks and then see if the old cases shoot better again.

 

[Jinx-)]

Annealing, well very interesting idea, looks like this brass has exhaust itself, I went through my records and it looks like I used it 10 times already. I guess the best course of action here is to start on the new batch, which I did, I'll leave old brass for later when I'll have time to do this annealing, which I never done it, looks like it will require some sort of crayon which changes colors... Anyway thank you for advice.

 

[Pdvdh]

There are some historical threads on annealing case necks on this Forum. Run a search. The last one I saw was getting the necks hotter than I do. With a propane torch held at the junction of the neck and shoulder, I twist my cases in a battery powered drill for about 5 1/2 seconds. Then dip the case neck quickly in ice water. I've use a Lee case holder to hold the case head and chuck it up in my 14.4 volt battery powered drill. Then spin the case/shoulder in the propane flame for 5 1/2 seconds. I keep a clock with a second hand on the table for purposes of timing the heating cycle. 5 1/2 seconds is about right with the hottest tip of the flame adjusted to be about 3/4" out from the torch head. Then quickly dunk in the ice water to prevent heating up the case head area. Deprime the cases before annealing so you don't have any pressure or suction formed inside the case when you dunk the case mouth into the ice water.

Simple as that. I determined the 5 1/2 seconds based on the use of the temperature crayons, plus the shade of the case necks after the annealing process. Also talked with Ken Markle of K&M Services and he told me on his propane torch he'd found about 5 to 5 1/2 second to be correct. That basically matched my findings also. The case should not be glowing red hot at all or you've overcooked the brass way too much. And the case neck will always be mushy soft after that. Practice on some throw away brass cases a little before you anneal your keeper cases. It's really not that difficult. But to do it the way I do it, you need the case to be held securely in the case holder that gets chucked into the battery operated drill.

Good luck.

 

[J E Custom]

There will always be the exception and some virgin brass will shoot great groups as long
as you have a tight chamber.

I prefer a very tight chamber for many reasons and one is longer brass life.

If the new/virgin brass fits well and has been prepped well it should do fine.I like to
neck turn before I fire it the first time because the chamber is the most concentric
place to form the brass near perfect and if you use brass that has a difference as much
as jrob mentioned when it is fired it will cause the cases to be eccentric from then on.

I hunt and shoot long range and if I'm going to enter a match or go on a hunt I prefer to
use once fired brass to make my loads because it is proven and fits my chamber perfect.

It may not be nessary but I feel it does make a deference and confidence all ways helps.

The method I use is =Weight sort in .5gr batches after sizing,trimming,deburring the primer
flash hole and out side neck turning and then load test in the new brass and if it is very
accurate I will use it for short to mid range matches and hunting and then load the once
fired brass that was used for testing and short range use to load my long range loads.

If your chamber is a factory chamber then chances are that it is very loose because they
chamber this way so that it will take any ammo with out feeding problems. and these
loose chambers should be fire formed and sized only enough to be chambered again.

I don't know if I helped you any but this is long range hunting/shooting and any small
advantage should be used if possible to improve the outcome of a long shot.

Just my opinion for what it's worth.

J E CUSTOM

 

[Jinx-)]

Ok but my brass was annealed at least it looked like it was at the factory, so how many times can this process be repeated
Thanks

 

[woods]

There may be other issues at play here. Last time I talked to one of the Sierra tech guys, I mentioned that I had just bought 300 rds. of Win. brass and had to neck turn it because it varied from .0115 to .017 on the necks. He asked me if I fireformed my brass. I thought, "Huh?" I only thought those AI guys did that stuff. He told me that he had 7mm Mag. brass that was on its 18th or 19th firing (I forget)because the first time he fired it, he loaded the bullets into the lands so that the case did not stretch above the belt.

According to him, if you don't put the bullet in the lands the first firing, the firing pin pushes the case forward to the shoulder (w/ virgin win. brass that's a long way) the case expands upon ignition and grips the walls of the chamber, then the case stretches above the belt (I imagine non-belted cases do the same thing) as the base of the case is rammed back into the bolt face. Seems very dramatic.

Have you guys heard of this. Makes sense on paper. Seems like a lot of work. I'm poised with 300 virgin brass. Do I fireform or not?

Thanks

John

Hey John

In the example where he said the firing pin pushes the case forward to the shoulder, that would not apply with a belted case. I have measured the amount of case travel in a few belted case chambers (headspace) and it varied from .000" to .007" because the belt stops forward movement. Now there is still significant space between the case shoulder and the chamber shoulder in the belted mags which is called "head clearance" and that can be as much as .030". But with the case forward movement stopped, it is not true that the firing pin pushes the case forward to contact. In a belted case the brass has to expand forward toward the shoulder.

In an unbelted case the firing pin and the explosion of the primer pushing on the inside of the primer hole propels the case forward to contact at the shoulder immediately and the case expands backward to the bolt face. There is usually significantly less headspace on an unbelted case than there is head clearance on a belted one. Someone mentioned .020" on a 30-06 case and that is more than it should be on an unbelted case. On my 30-06, the headspace generally ranges from .010" to .012" depending upon the brass.

Also, if your neck thicknesses vary from .0115" to .017" you have a problem. Even with outside neck turning you are not going to do a lot of good with those case. Reference this diagram that shows how neck turning will not correct a problem of too much neck thickness variation

If I were you I would separate the cases based upon neck thickness variation. Those with little to no variation are worth your trouble to neck turn (.002" or less), but those with the large variations will continue to degrade your accuracy.

As far as new vs. fire formed, I get my best accuracy and consistancy with fire formed partial full length resized but only when I pay attention to consistant bullet release. That means cleaned, steel wooled, mica'ed and annealed when necessary.

JMHO

 

[J E Custom]

Hey John

In the example where he said the firing pin pushes the case forward to the shoulder, that would not apply with a belted case. I have measured the amount of case travel in a few belted case chambers (headspace) and it varied from .000" to .007" because the belt stops forward movement. Now there is still significant space between the case shoulder and the chamber shoulder in the belted mags which is called "head clearance" and that can be as much as .030". But with the case forward movement stopped, it is not true that the firing pin pushes the case forward to contact. In a belted case the brass has to expand forward toward the shoulder.

In an unbelted case the firing pin and the explosion of the primer pushing on the inside of the primer hole propels the case forward to contact at the shoulder immediately and the case expands backward to the bolt face. There is usually significantly less headspace on an unbelted case than there is head clearance on a belted one. Someone mentioned .020" on a 30-06 case and that is more than it should be on an unbelted case. On my 30-06, the headspace generally ranges from .010" to .012" depending upon the brass.

Also, if your neck thicknesses vary from .0115" to .017" you have a problem. Even with outside neck turning you are not going to do a lot of good with those case. Reference this diagram that shows how neck turning will not correct a problem of too much neck thickness variation

If I were you I would separate the cases based upon neck thickness variation. Those with little to no variation are worth your trouble to neck turn (.002" or less), but those with the large variations will continue to degrade your accuracy.

As far as new vs. fire formed, I get my best accuracy and consistancy with fire formed partial full length resized but only when I pay attention to consistant bullet release. That means cleaned, steel wooled, mica'ed and annealed when necessary.

JMHO

Not trying to pick a fight so don't take this wrong.

On the neck thickness issue = If you have a proper fitting mandrel/pilot for the inside neck dia.
and you turn them correctly you will end up with case necks as close to perfect as possible and
most would agree that if you get within 1 or 2 ten thousandths then you are there. I have found
this to be the best way to address this problem before it is fired.

And the head space issue scared me and I think you made a mistake with the dimensions
because the Absolute maximum allowable head space on any type of cartridge is .008 (The
dimension of a No Go Gauge !!!

Belted cases should have no more head space than .003 and non belted cases should have no
more than .001 to .003 for accuracy and brass life.

If you have more head space than .006 to .008 you run the risk of having case head separation
and that is not good.

If your 3006 has .010 to .012 head space you need to back way off on the sizing die or neck
size only. I have never had a case head separation and don't intend to because I have seen
many matches and hunts ruined by head separation.

Also on any case you should not have any more space in front of the case than the head space
If yo do the chamber was not reamed correctly or it was not a SAAME spec. reamer.

When fire forming a case from a standard case to a wild cat this could be the case but that
requires reduced loads for safety.

J E CUSTOM

 

[Jinx-)]

Back to annealing, how many times can brass be annealed? If it's already annealed like Lapua brass can I do it again after 10 neck sizing?
Thanks

 

[woods]

Hey JE

A go-no-go gauge does measure the headspace on a belted case and in my explanation I said that in my measurements on headspace on the belted mags they varied from .000" to .007". That is measured from the case head to the front of the belt, or technically it is the gap between the case head and the bolt face when the belted case is seated as far forward as it will go in the chamber. The belt stops it, not the shoulder. So a go-no-go gauge will measure that headspace and it will not give you any indication of the remaining gap between the case shoulder and chamber shoulder. IOW you could easily have a headspace measurement with a go-no-go gauge of .003" and still have a head clearance measurement of .030" with a more useful gauge such as the Hornady Headspace Gauge which gives you measurements from the case head to the case shoulder, even on a belted case.

The measurement on my 30-06 was the difference between the headspace measurements taken by the Hornady on NEW cases and FULLY EXPANDED cases at the datum line. I DO NOT repeatedly full length size and DO NOT need to back off on on my sizing dies. They are set to push the shoulder back .001" from a crush fit EVERYTIME AFTER THE CASES HAVE EXPANDED. I can not however do anything about the undersize dimensions of NEW CASES since I do not have multiple hydraulic form dies and refuse to downsize cases with larger dimensions in order to preset the shoulder at a specific location on a new case. I do not make my own brass so I am stuck with what I can get just like everyone else.

The illustration was to show how a case that has a large neck variation from side to side will continue to have it's neck off center in relation to the center of the case body even after neck turning. Perhaps there are some exceptions to this, I would be happy to listen to them. I did not say that he should not neck turn anyway, just that neck turning will not solve and off center poor piece of brass. I also neck turn on new cases for several calibers.

JE, do you have a Hornady Headspace Gauge or only a go-no-go? Not trying to pick a fight so don't take this wrong, but if you do not have a Hornady Gauge then perhaps you should get one and measure the distance from the case head to the datum line on a new case for a belted mag and then measure that same distance once you fire it. Do it on a gun that your go-no-go says has a headspace between your tolerances. The excess clearance at the shoulder will surprise you and is as much a problem with the brass manufacturers as it is with the gun manufacturers.

Here are some measurements I have taken with the Hornady

rifle / new case / fully expanded case / head clearance
Mato 338 win mag / 2.0970" / 2.1240" / .027"
Sako 300 win mag / 2.2530" / 2.2735" / .0205"
Mato 300 win mag / 2.2530" / 2.2725" / .0195"
Pre-64 264 win mag / 2.109" / 2.1385" / .0295"
Win 70 264 win mag / 2.088" / 2.1290" / .0410"
Custom 6.5 rem mag / 1.768" / 1.785" / .017"

All of these guns had headspace between .000" and .007". I have since rebarreled the 338 Mato and the Win 264 and sold the pre-64 Win 264 because of their excess head clearance.

Something I noticed on my 7mm Rem Mag brass - Topic Powered by Eve Community

If gunsmiths would ream the chambers to match new brass as Saeed mentions in the above thread then the incidence of case head separations would be greatly reduced.

 

[padd54]

Jinx, if you would stop yelling, perhaps someone would address your question.